The major difference between symbolic interactionism and the two macro-level perspectives in sociology is that the macro-level perspectives look at large chunks of society or at society as a whole while symbolic interactionism looks at individual people and their internal lives. In short, symbolic interactionism is a micro-level perspective while the others are, as you say, macro-level.
The two macro-level perspectives are not terribly interested in what individual people do. Instead, they are interested in what large groups do. For example, a functionalist might try to understand why women tend not to advance as far in the workplace as men do. A conflict theorist might attempt to explain why non-whites are generally less wealthy than whites. These questions look at large groups in society, not at the way that individuals think.
By contrast, symbolic interactionism does look at what individuals think. This perspective says that society is created by the ways in which people interact with the world around them. Individuals in society have to look at all the things that go on around them and assign meaning to those things. They have to essentially treat things like other people’s actions and words as symbols. They do the same to other things like flags, crosses, pictures of Santa Claus and anything else you might think of. People see those things and give them meaning. They then interact with those meanings, letting the meanings that they assign to those things influence their lives. Symbolic interactionism is interested in this process of thinking about the world that goes on inside people’s heads. This makes it very different from the other two perspectives.